e-Xtra* Resistance of Sharon Goatgrass ( sharonensis) to Fungal Diseases of Wheat

P. D. Olivera, Department of Pathology, University of Minnesota, St. Paul 55108; J. A. Kolmer, United States Department of Agriculture–Agricultural Research Service, Cereal Disease Laboratory, Department of Plant Pathol- ogy, University of Minnesota, St. Paul 55108; Y. Anikster, Institute for Cereal Crops Improvement, Tel Aviv Univer- sity, Ramat Aviv, Israel 69978; and B. J. Steffenson, Department of Plant Pathology, University of Minnesota, St. Paul 55108

breeders must be vigilant for virulence ABSTRACT changes in the stem rust population. For Olivera, P. D., Kolmer, J. A., Anikster, Y., and Steffenson, B. J. 2007. Resistance of Sharon goat- example, in 1999, a new race of P. grass (Aegilops sharonensis) to fungal diseases of wheat. Plant Dis. 91:942-950. graminis f. sp. tritici (race TTKS or isolate Ug99) was discovered in eastern Africa Sharon goatgrass (Aegilops sharonensis) is a wild relative of wheat that is native to Israel and that possesses virulence for many of the Lebanon. The importance of A. sharonensis as a source of new resistance genes for wheat war- wheat cultivars grown in the Great Plains rants additional research on the characterization of accessions for economically important genes. region (48). The introduction of such a Thus, the objectives of this study were to evaluate a collection of A. sharonensis accessions for race into the United States will have devas- resistance to seven important fungal diseases of wheat and assess the phenotypic diversity of the germplasm for disease reaction. The frequency of resistance in A. sharonensis was highest to tating consequences. Stripe rust is another powdery mildew (79 to 83%) and leaf rust (60 to 77%). Resistance to stem rust also was com- important rust disease of wheat, particu- mon, although the percentage of resistant accessions varied markedly depending on the pathogen larly in the cool and moist regions of the race—from 13% to race TTTT to 72% to race QCCJ. The frequency of resistance was interme- Pacific Northwest. Since 2000, however, diate to stripe rust (45%) and low to tan spot (15 to 29%) and spot blotch (0 to 34%). None of this rust disease has become increasingly the A. sharonensis accessions was resistant to Fusarium head blight. Many of the accessions important in the south-central states and tested exhibited heterogeneous reactions (i.e., had both resistant and susceptible ) to one or central Great Plains, a region previously more of the diseases, suggesting that heterozygosity may be present at some resistance loci. considered noncongenial to the pathogen Substantial variation was observed in the level of diversity to individual diseases because Shan- (9). Total yield losses to stripe rust in the non’s Equitability index ranged from 0.116 (for Fusarium head blight) to 0.994 (for tan spot). A United States in 2003 were estimated at 86 high level of diversity was found both between and within collection sites. Moreover, differences million bushels (4.8% of wheat produc- in the geographic distribution of resistant accessions were observed. For example, accessions tion), making it the most important rust from northern Israel generally were less diverse and less resistant to leaf rust and stripe rust than disease of wheat over the past few years accessions from more southern locations. Four A. sharonensis accessions were highly resistant to (33). Two other diseases that have in- most of the diseases evaluated and may provide a source of unique resistance genes for intro- gression into cultivated wheat. creased in incidence and severity during the last decade are tan spot (Pyrenophora Additional keywords: disease resistance, wild wheat tritici-repentis (Died.) Drechsler, ana- morph Drechslera tritici-repentis (Died.) Shoemaker) and spot blotch (Cochliobolus sativus (S. Ito & Kurib.) Drechsler ex Das- Bread wheat (Triticum aestivum L.) is limited by both biotic and abiotic con- tur, anamorph: Bipolaris sorokiniana one of the most important cereal crops, straints. Disease is the major biotic stress (Sacc.) Shoemaker). The increased severity providing about 20% of the food calories in many regions. More than 200 diseases of these diseases has been favored by the consumed by people worldwide (65). In have been described on wheat, 50 of which wide adoption of minimum tillage and the United States, wheat is the third most are considered economically important retention of crop residues on the soil sur- widely grown crop behind corn and soy- (65). face (12). Although it is not a serious prob- bean and is cultivated on 25 million ha The major fungal diseases of wheat in lem of wheat in the main production re- (44). Wheat production can be severely the United States include Fusarium head gions of the United States, powdery blight (FHB) (caused primarily by Fusa- mildew (Blumeria graminis (DC.) Speer. f. Corresponding author: B. J. Steffenson rium graminearum Schwabe, teleomorph: sp. tritici Em. Marchal) has caused signifi- E-mail: [email protected] Gibberella zeae (Schwein.) Petch), leaf cant losses (up to 17%) in winter wheat in rust (Puccinia triticina Erikss.), stem rust the southeastern Atlantic coast states (32). * The e-Xtra logo stands for “electronic extra” and (P. graminis f. sp. tritici Erikss. & Hen- Although fungicide treatments have be- indicates that two supplemental tables not included ning), and stripe rust (P. striiformis f. sp. come a common practice in cultivated in the print edition are available online. Table 1 contains the complete set of raw infection pheno- tritici Erikss.). In the last decade, FHB has wheat, the increasing environmental con- type data of Aegilops sharonensis accessions to become one of most significant plant dis- cerns regarding their use make the de- seven wheat fungal diseases, and Table 2 gives the eases in the United States, causing losses ployment of resistant wheat cultivars an numbers of different reactions to seven pathogens exceeding $2.5 billion (66). Rusts also can attractive and economically sound alterna- in Aegilops sharonensis accessions according to be significant in reducing yield. During the tive for disease control. The use of resis- collection site. last 20 years in the United States, leaf rust tant cultivars to control diseases requires Accepted for publication 17 February 2007. has been prevalent in all wheat-production the availability of many sources of resis- areas, causing yield losses between 1 and tance to counter the continuing evolution 8% (33). Although stem rust has not been a of new virulence types in pathogen popula- doi:10.1094/ PDIS-91-8-0942 major problem of wheat in the central and tions (21). From the time of first domesti- This article is in the public domain and not copy- northern Great Plains during the last 40 cation, the genetic diversity of wheat has rightable. It may be freely reprinted with custom- ary crediting of the source. The American Phyto- years, it is still considered the most de- been seriously eroded. Thus, it is impera- pathological Society, 2007. structive cereal rust (49). Pathologists and tive that the wheat gene pool be expanded

942 Plant Disease / Vol. 91 No. 8 by incorporating new genes into breeding in some A. sharonensis populations is at information. The Israeli accessions came programs (21). In this regard, wild wheat risk (43). from 11 collection sites covering most of relatives offer one of the most diverse The importance of A. sharonensis as a the known distribution area of the sources of unique alleles for wheat im- source of resistance is well documented. within the country (43) (from 34.9° to provement (46). Previous investigators have identified in 36.4°N latitude), including the regions of Aegilops is the genus most closely re- the species sources of resistance to leaf Haifa Bay (3% of the accessions), Central lated to Triticum (25,26) and comprises 23 rust (4,5,21,37,46), stem rust (19), powdery Coastal Plain (40.2% of the accessions), species that include diploid, tetraploid, and mildew (21,46), Karnal bunt (64), Hessian and Southern Coastal Plain (56.8% of the hexaploid genomes (61). Aegilops spp. fly (21), and greenbug (21). The results accessions) (Fig. 1; Table 1). These popu- such as Aegilops umbellulata, A. spel- from all studies suggest that a high level of lations reflect the typical habitats of A. toides, A. squarrosa, A. longissima, and A. diversity for resistance exists in the species. sharonensis in Israel. The altitude at the comosa are known to be rich sources of In spite of the many examples of pathogen collection sites ranged between 0 and 100 resistance to various pathogens and pests and pest resistance in A. sharonensis, suc- m above sea level. Each accession within a (2,4,5,10,21,37,46,57,64), and many resis- cessful introgression of resistance genes collection site in Israel was derived from a tance genes have been transferred to into cultivated wheat has been reported only single spike gathered at least 5 m apart wheat. Some of the most important ones for leaf rust and stripe rust (38,39). along a straight transect. No information include Lr9, Lr21, Lr22, Lr28, and Lr35 The importance of A. sharonensis as a was available about the collection sites or for leaf rust resistance; Sr32, Sr34, and source of resistance genes for wheat, to- sampling technique of the accessions pro- Sr39 for stem rust resistance; Yr8 for stripe gether with its threatened habitats, warrant vided by CIMMYT or the NSGC. Prior to rust resistance; Pm13 for powdery mildew additional research on the collection of disease evaluation, all accessions were resistance; and Gb5 for greenbug resis- additional accessions and their characteri- grown for seed increase in a nethouse and tance (17,56). zation for economically important genes. greenhouse. A. sharonensis Eig (Sharon goatgrass) is The objectives of this study were to evalu- Pathogen isolates. Information about another potentially rich source of resis- ate a collection of A. sharonensis acces- the fungal pathogens used in the disease tance genes for wheat (4,5,21,37,46,64), sions for resistance to seven important phenotyping tests is summarized in Table but has not been exploited to any great fungal diseases of wheat and assess the 2. Three races of Puccinia triticina were extent for wheat improvement. This spe- phenotypic diversity of the germplasm for used. Race BBBB possesses the narrowest cies is diploid (2n = 2x = 14, with a Sl or disease reaction. virulence spectrum of any culture in the Ssh genome formula) and belongs to the USDA-ARS Cereal Disease Laboratory section Sitopsis of the genus Aegilops (61). MATERIALS AND METHODS collection. BBBB was selected because it It is, like all members of the section Sitop- Germplasm. In all, 107 accessions of A. may have the potential to detect the pres- sis, part of the secondary gene pool of sharonensis from Israel and Lebanon were ence of more resistance genes in the A. wheat, sharing homoeology with the wheat evaluated in this study. All but five of these sharonensis accessions. In contrast, race genome (17,25). A. sharonensis originated accessions were from Israel. The Israeli THBJ has a wider spectrum of virulence and appears to be endemic only in the accessions were from the Harold and and also is one of the most common races coastal plain of Israel and in a few loca- Adele Lieberman Germplasm Bank in the found in the Great Plains (28,35). Race tions in southern Lebanon (26,29,61), a Institute for Cereal Crops Improvement at THBJ was included because it is virulent very limited geographical area that extends Tel Aviv University. Four accessions were for many wheat Lr genes and possibly may for about 210 km north to south and no from Lebanon and provided by Thomas identify within A. sharonensis any genes more than 15 km east from the Mediterra- Payne (Centro Internacional de Mejo- that are potentially valuable for wheat nean Sea (43). A. sharonensis grows in the ramiento de Maiz y Trigo [CIMMYT], El improvement. Race PNMQ was selected most highly populated area of Israel, Batan, Mexico). One accession provided because it has a different virulence spec- where agriculture and urbanization are by Harold Bockelman (United States De- trum than BBBB and THBJ and, therefore, rapidly replacing its natural habitat partment of Agriculture–Agricultural Re- can identify other genes not selected by (29,43). Thus, the genetic diversity present search Service [USDA-ARS], National these other races. All leaf rust races were Small Grain Collection [NSGC], Aber- verified for their virulence phenotype (34), deen, ID) originally came from the Aegean purified, and then increased on seedlings Agricultural Research Institute Genebank of the susceptible wheat cv. Thatcher (Cltr (Izmir, Turkey), but without any passport 10003).

Table 1. Number and origin of Aegilops sharonensis accessions used in this study Location Coordinatesz Number of accessions Israel Haifa Bay 3 1. En HaMifraz 36.69E/36.42N 3 Central Coastal Plain 41 2. Hefzi Bah 36.68E/35.93N 9 3. Mikhmoret 36.68E/35.88N 2 4. Kefar Ganim 36.67E/35.50N 8 5. Qiryat Ono 36.67E/35.49N 2 6. Palmahim 36.66E/35.34N 13 7. Ben Zakkai 36.64E/35.26N 7 Southern Coastal Plain 58 8. Ashdod 36.65E/35.23N 33 9. HaShikmim Park 36.65E /35.17N 5 10. Nizzanim 36.65E/35.12N 10 11. Ziqim 36.64E/34.98N 10 Lebanon –/– 4 Fig. 1. Map of Israel showing the location of the Aegilops sharonensis collection sites. z From Millet et al. (43); – indicates data not available.

Plant Disease / August 2007 943 Four races of P. graminis. f. sp. tritici tions on the spot blotch differential lines of tion, plants were evaluated for their ITs were selected for this study based on their barley (15,60) and also on certain wheat based on the 0-to-4 scale of Long and differential virulence phenotype or impor- accessions. Kolmer (34). Wheat cv. Thatcher (Cltr tance in agriculture. Race TTTT is the Isolate KB-172 of F. graminearum was 10003) was used as the susceptible control. most widely virulent race known in the used for the FHB evaluations. This isolate Stem rust. The inoculation protocol used United States and produces high infection originally was collected from barley in for stem rust was the same as described for types (ITs) on all of the wheat stem rust North Dakota in 1994. It is highly virulent leaf rust with two exceptions: (i) the spore differential lines (50). Race TTKS origi- on barley and wheat and a reliable pro- concentration used was approximately nated in eastern Africa and is virulent for ducer of deoxynivalenol (DON) (53). 0.028 mg of spores per plant and (ii) plants Sr31, a widely used gene in wheat culti- Inoculation protocols and disease as- were exposed to light during the last 5 h of vars worldwide (48). Race TPMK was the sessment. Plants were evaluated to leaf the misting period, a requirement for the predominant race in all areas of the United rust and stem rust at both the seedling and Puccinia graminis f. sp. tritici infection States during the 1990s (41). Race QCCJ adult plant stages; to stripe rust, tan spot, process (52). Twelve days after inocula- has a markedly different virulence spec- spot blotch, and powdery mildew at the tion, plants were evaluated for their ITs trum and, therefore, can identify other seedling stage only; and to FHB at the based on the 0-to-4 scale of Roelfs et al. genes not distinguished by the other races. adult plant stage only. All experiments (51). Wheat cv. McNair 701 (Cltr 15288) All races were verified for their virulence were done in a completely randomized was used as the susceptible control. phenotype (50), purified, and then in- design with one replicate and were re- Stripe rust. The inoculation protocol for creased on the susceptible wheat cv. peated once. The disease evaluation tests stripe rust was the same as described for McNair 701 (Cltr 15288). were performed between summer 2003 leaf rust. After inoculation, plants were Race PST-78 of P. striiformis f. sp. and winter 2006. transferred to a mist chamber at 10°C and tritici was used for the stripe rust evalua- Seedling evaluations. To obtain uni- approximately 100% RH for 24 h. Then, tion because it is the most predominant form germination of the A. sharonensis plants were placed in a growth chamber race in the United States (9). Uredinio- accessions, seed was removed from the programmed to change temperature gradu- spore increases were made on the suscep- spikelets and germinated on filter paper ally from 4°C at 0200 h to 18°C at 1400 h tible wheat cv. Express (PI 573003). moistened with distilled water in 9-cm with a 16-h photoperiod between 0600 and Two isolates (UM05-01 and UM06-01) petri plates (37). Seed were incubated at 2200 h (9). ITs were assessed 19 to 22 of B. graminis f. sp. tritici were used for 4°C for 7 days and then at 22 to 25°C for 1 days after inoculation using the 0-to-4 the powdery mildew evaluations. Both day. Five seeds of each accession were scale of McIntosh et al. (40). Wheat cv. isolates were derived from individual sin- planted in plastic cones (3.8 cm in diame- Express (PI 573003) was used as the sus- gle pustules collected in the greenhouse at ter by 21 cm in depth) containing soil and ceptible control. the University of Minnesota, verified for Metromix 200 (vermiculite, peat moss, Powdery mildew. Seedlings were inocu- their virulence phenotype (23), and then perlite, and sand mix) in a 60:40 ratio. lated by shaking mildew-infected plants of increased on the susceptible wheat cv. Seedlings were inoculated at the second- wheat cv. Roblin (four-leaf stage) over the Roblin. leaf stage, 12 to 14 days after planting. test entries. Inoculated plants then were Two races of Pyrenophora tritici- Leaf rust. Seedlings were inoculated kept in the greenhouse at 22 to 28°C. Eight repentis (race 1 and race 5) were used for with urediniospores suspended in a light- days after inoculation, plants were evalu- the tan spot evaluations. Race 1 is preva- weight mineral oil (approximately 0.014 ated for their ITs using the 0-to-4 scale of lent in the Great Plains region of the mg of spores per plant). Following inocu- Mains and Dietz (36). Wheat cv. Roblin United States (3) and produces two host- lation, plants were transferred to mist was used as the susceptible control. specific toxins, Ptr ToxA and Ptr ToxC chambers and incubated for 16 h in dark- Tan spot. An inoculum concentration of (31). Race 5 produces the host-specific ness at 18 to 21°C and approximately 3 × 103 conidia/ml (plus one drop of toxin Ptr ToxB (31). Both races induce 100% relative humidity (RH) (37). After Tween 20 per 0.5 liters of suspension) was chlorotic and necrotic reactions on wheat. the mist period, plants were allowed to used for the tan spot inoculations (2). In- Two races of C. sativus (race 0 and race slow dry for 4 h before being placed in a oculum was applied to seedlings at a rate 2) were used for the spot blotch evalua- growth chamber at 18 to 21°C with a 14-h of approximately 0.08 ml/plant using an tions. These races exhibit differential reac- photoperiod. Twelve days after inocula- artist’s airbrush (Model H & HS; Paasche

Table 2. Race or isolate designation, virulence phenotype, and source of wheat fungal pathogens used to evaluate resistance in Aegilops sharonensisx Pathogen Race Isolate Virulence/avirulence formulay Sourcez Puccinia triticina THBJ 99ND588DLL 1, 2a, 2c, 3a, 16, 26, 10, 14a, 18/9, 24, 3ka, 11, 17, 30, B J. Kolmer, USDA St. Paul P. triticina PNMQ 94LA101 1, 2c, 3a, 9, 24, 3ka, 30, B, 10/2a, 16, 26, 11, 17, 14a, 18 J. Kolmer, USDA St. Paul P. triticina BBBB NA –/1, 2a, 2c, 3a, 9, 16, 24, 26, 3ka, 11, 17, 30, B, 10, 14a, 18 J. Kolmer, USDA St. Paul P. graminis f. sp. tritici TTTT 02MN84A-1-2 5, 21, 9e, 7b, 11, 6, 8a, 9g, 36, 9b, 30, 17, 9, 9d, 10, Tmp/– Y. Jin, USDA St. Paul P. graminis f. sp. tritici TTKS 99UGA 5, 21, 9e, 7b, 11, 6, 8a, 9g, 9b, 30, 17, 9a, 9d, 10/36, Tmp Y. Jin, USDA St. Paul P. graminis f. sp. tritici TPMK 95NE115-A 5, 21, 9e, 7b, 11, 8a, 9g, 36, 17, 9d, 10, Tmp/6, 9b, 30, 9a J. Kolmer, USDA St. Paul P. graminis f. sp. tritici QCCJ 01TX27C 5, 21, 9g, 17, 9d, 10/9e, 7b, 11, 6, 8a, 36, 9b, 30, 9a, Tmp J. Kolmer, USDA St. Paul P. striiformis f. sp. tritici PST-78 NA 1, 3, 11, 12, 16, 17, 18, 19, 20/2, 4, 5, 6, 7, 8, 9, 10, 13, 14, 15 X. Chen, USDA Pullman Blumeria graminis f. sp. tritici NA UM05-01 1a, 2a, 3a, 3c, 3e, 3f, 5a, 6, 7, 8/3b, 4a, 4b, 9, 17, 25 P. Olivera, Univ. of MN B. graminis f. sp. tritici NA UM06-01 1a, 2a, 3b, 3c, 3e, 5a, 6, 7, 8, 9/3a, 3f, 4a, 4b, 17, 25 P. Olivera, Univ. of MN Fusarium graminearum NA KB172 NA B. Steffenson, Univ. of MN Pyrenophora tritici-repentis 1 Asc1 … L. Lamari, Univ. of Mba. P. tritici-repentis 5 Alg3-24 … L. Lamari, Univ. of Mba. Cochliobolus sativus 0 ND93-1 … B. Steffenson, Univ. of MN C. sativus 2 ND 90Pr … B. Steffenson, Univ. of MN x NA = not applicable or not available. y – Indicates no differential in the virulence or avirulence category, and … = resistance genes for all of the differential genotypes have not been characterized. z USDA = United States Department of Agriculture–Agricultural Research Service; St. Paul = Cereal Disease Laboratory. St. Paul, MN; Pullman = Wheat Genetics, Physiology, Quality, and Disease Research Unit, and Department of Plant Pathology, Washington State University, Pullman; Univ. = University; MN = Minnesota; and Mba. = Manitoba, Canada.

944 Plant Disease / Vol. 91 No. 8 Airbrush Company, Chicago) pressurized plant. The incubation protocols were the sity, 0.85 to 0.50 of intermediate diversity, by a CO2 tank at 138 kPa. After inocula- same as described for the seedling tests. and <0.50 of low diversity. Both analyses tion, plants were placed in a mist chamber Plants were evaluated for their leaf rust were performed using the three general for 16 h at 18 to 22°C and approximately response using the modified Cobb scale reaction classes of resistant, intermediate, 100% RH (30). Following the mist period, (47). For stem rust, inoculations were made and susceptible. inoculated plants were allowed to dry for 4 at the heading stage on the upper two inter- h and then placed in a growth chamber at nodes of each plant with a urediniospore RESULTS 20 to 23°C with a 14-h photoperiod. Plants suspension (8.0 mg per 0.7 ml of oil) at a Infection phenotypes of the differential were evaluated for their IT 8 days after rate of approximately 0.8 mg/plant. Again, host lines used to assign pathotypes of inoculation using the scale of Lamari and the infection period protocols were the same each pathogen were consistent with previ- Bernier (30). Wheat differential lines as described for the seedling tests. At 12 to ously published results (data not shown). 6B635, Katepwa, Erik (PI 476849), Coulter 14 days after inoculation, plants were evalu- The same was true for the controls in- (Cltr 17757), 6B662, Salamouni (PI ated for their infection response using the cluded in each experiment. Overall, the 182673), Glenlea (Cltr 17272), and 4B1149 scale of Roelfs et al. (51). infection phenotypes of the A. sharonensis were used as the controls (31). FHB. For FHB evaluations, the spray accessions to each of the respective patho- Spot blotch. The inoculum concentration and needle injection inoculation techniques gen races or isolates were similar between used for the spot blotch inoculations was 6 were applied to identify resistance to initial the two replicates of each experiment. to 8 × 103 conidia/ml (60) (plus one drop infection (i.e., type I) and resistance to Among all the pathogens evaluated, the of Tween 20 per 0.5 liters of suspension). spread (i.e., type II), respectively (11). highest percentage of resistance found in Inoculum was applied at a rate of ap- Both inoculations were done when plants A. sharonensis was to B. graminis f. sp. proximately 0.08 ml/plant with an artist’s were at 30 to 50% anthesis using a concen- tritici (79.4 and 83.2% for isolates UM05- airbrush as described above. After inocula- tration of 4 × 105 macroconidia/ml (11). 01 and UM06-01, respectively; Table 3). tion, plants were placed in a mist chamber For the single floret inoculation, a metered Most (87 and 94%) of these resistant ac- for 16 to 18 h in the dark at 18 to 22°C and hypodermic syringe (Model PB600; Ham- cessions exhibited very low ITs of 0 and 0; approximately 100% RH. Following the ilton Company, Reno, NV) was used to indicating a very high level of resistance. mist period, plants were allowed to slow inject 5 µl of inoculum into each of the two Only 2 (1.9%) and 3 (2.8%) accessions dry before being placed into a growth central spikelets of the spike. For spray were heterogeneous in their IT to the re- chamber at 21 to 23°C with a 16-h photo- inoculation, approximately 0.7 ml of in- spective isolates, suggesting a very low period. Seedlings were assessed for their oculum/spike was delivered using an art- level of heterozygosity at the resistance ITs 6 and 8 days after inoculation. A 0-to-5 ist’s airbrush as described previously. After loci. The percentage of resistance to P. scale adapted from Adlakha et al. (1) was inoculation, plants were transferred to a triticina was similarly high at the adult used for assessing the ITs, where 0 = no mist chamber at 18 to 21°C and approxi- plant stage to races THBJ (76.6%) and visible sign of infection, 1 = pinpoint le- mately 100% RH for 40 h. Following the PNMQ (77.4%) (Table 3). Again, most (73 sions, 2 = small lesions, 3 = medium le- mist period, inoculated plants were placed and 69%) of these resistant accessions sions, 4 = large lesions, and 5 = very large in a greenhouse at 17 to 28°C with a 14-h were highly resistant, giving ITs of 0;. At lesions showing coalescence. Barley cv. photoperiod. FHB assessments were made the seedling stage, the percentage of acces- Bowman (PI 483237) and barley lines 14 and 21 days post inoculation by count- sions resistant to P. triticina was lower: ND5883 and ND B112 (CIho 11531) were ing the number of infected spikelets. FHB 59.8% to race BBBB and 62.6% for race used as controls (60). severity then was calculated by dividing THBJ. Heterogeneous leaf rust reactions For the rusts and powdery mildew, ITs the number of infected spikelets by the were found in 12.3 to 22.4% of the acces- from 0 to 1 were considered indicative of total number of spikelets in the spike. sions, the highest frequency being to race resistance, 2 of an intermediate reaction, Wheat cvs. Sumai 3 (PI 481542) and BBBB. This suggests a fairly high level of and 3 to 4 of susceptibility. For tan spot Wheaton (PI 469271) were the resistant heterozygosity for leaf rust resistance loci. and spot blotch, infection responses from 0 and susceptible controls, respectively. Although a higher frequency of leaf rust- to 2 were considered indicative of resis- For leaf rust and stem rust, IT R was resistant accessions was observed at the tance, 3 of an intermediate reaction, and 4 considered indicative of resistance, MR adult plant stage compared with the seed- to 5 of susceptibility. Accessions were and MS of an intermediate reaction, and S ling stage, the χ2 value obtained from the classified as heterogeneous if they clearly of susceptibility. For FHB, 0 to 25% infec- contingency table for race THBJ (seedling contained both resistant and susceptible tion was considered indicative of resis- versus adult plant stage) indicated a strong plants, resistant and intermediate plants, or tance, 25 to 50% as an intermediate reac- association in the reactions (Table 4). In susceptible and intermediate plants. tion, and 50 to 100% of susceptibility. addition, strong associations were found Adult plant evaluations. In all, 5 ger- Accessions were classified as heterogene- for the reactions elicited by all leaf rust minated seeds per accession were planted ous if they clearly contained both resistant races in pairwise comparisons. in peat pots (1 seed per pot) filled with soil and susceptible plants. Resistance to P. graminis f. sp. tritici and Metromix 200 at a 70:30 ratio. When Data analysis. The percentage of acces- also was common in A. sharonensis, al- the plants reached the three-leaf stage, they sions giving resistant, intermediate, sus- though the percentage of resistant acces- were transferred to a vernalization cham- ceptible, and heterogeneous reactions to sions varied markedly depending on the ber (4°C and 6-h photoperiod) for 6 weeks. each pathogen at the seedling stage was pathogen race. The highest percentage of Following vernalization, plants were trans- calculated. In addition, χ2 values were resistance found was in response to races planted into plastic pots (10 by 10 cm) calculated from contingency tables to as- QCCJ (72.0%) and TTKS (69.2%) and the filled with soil and Metromix 200 (70:30 sess the relationship of the reactions of A. lowest to races TPMK (32.7%) and TTTT ratio) and grown in a greenhouse at 18 to sharonensis to races within a pathogen (13.1%) in seedling plants (Table 3). The 25°C with a 14-h photoperiod until they (e.g., P. triticina races BBBB versus percentage of highly resistant accessions were inoculated. THBJ). Phenotypic diversity for disease (IT of 0; and 1) to stem rust in seedling Leaf rust and stem rust. For the leaf rust reaction in A. sharonensis was estimated plants also was lower than for leaf rust and evaluation, fully expanded flag, flag-1 and using the Shannon diversity index (hs), varied depending on the pathogen race flag-2 leaves were inoculated at the head- where hs = –Σpi ln(pi), with a maximum hs (28% for TTTT and QCCJ, 42% for ing stage with urediniospores suspended in = 1.099 (16). Values of Shannon’s equita- TTKS, and 57% for TPMK). The percent- mineral oil (4.0 mg per 0.7 ml of oil) at a bility (Eh) (Eh = hs/hmax) higher than 0.85 age of resistance to race TTTT was more rate of approximately 0.4 mg of spores/ were considered indicative of high diver- than three times higher at the adult stage

Plant Disease / August 2007 945 (41.7%) than at the seedling stage (13.1%); neous spot blotch reactions ranged from spectrum of resistance to the various however, the χ2 value obtained from the 3.7 to 9.3%, indicating a low to moderate pathogen races or isolates that were used contingency table indicated a significant level of heterozygosity for the resistance in this study. Accessions 2172 and 2173 association in the reaction to race TTTT at loci. The χ2 value obtained from the con- were similar in their reactions, being sus- the two growth stages (Table 4). The same tingency table indicated no association ceptible only to FHB, stripe rust, and race was true for pairwise comparisons of reac- between the reactions to race 0 and race 2 0 of C. sativus. Both accessions exhibited tions to races TTKS, TPMK, and QCCJ at of C. sativus (Table 4). None of the acces- an intermediate reaction to Puccinia the seedling stage (Table 4). Accessions sions was highly resistant to race 2, be- graminis f. sp. tritici race TTTT at seed- with heterogeneous stem rust reactions cause the lowest IT observed was 12. ling stage. Accession 591 also exhibited were observed, but at an overall lower Accessions with resistance to F. resistant reactions to most of the pathogen frequency (1.2 to 12.1%) than found with graminearum were not identified in A. isolates, but was intermediate to race 0 of leaf rust. sharonensis, and only 2.8% of the acces- C. sativus, race TTKS of P. graminis f. sp. Nearly 45% of the accessions were re- sions exhibited an intermediate reaction tritici, and race 5 of Pyrenophora tritici- sistant to P. striiformis f. sp. tritici (Table (Table 3). Heterogeneous reactions were repentis, and was susceptible only to FHB. 3). Of these resistant accessions, 89% were not observed for any accession in response Accession 1644 was susceptible only to highly resistant, giving low ITs of 0; to 1. to this pathogen. FHB and spot blotch, and was intermediate In all, 13.1% of accessions were heteroge- The A. sharonensis accessions 2172, in its reaction to race 1 of P. tritici- neous in their reactions to stripe rust, a 2173, 591, and 1644 exhibited the broadest repentis. level comparable with that observed with the other two rust pathogens at the seed- ling stage. Table 4. Probability and χ2 values from contingency tables for associations of the reactions of Ae- Although the frequency of resistant plus gilops sharonensis accessions to various pathogens, pathogen races, and ontogenetic stages intermediate accessions was similar (ap- Association between proximately 60%) to both races of Pyreno- phora tritici-repentis, the frequency of Fungal pathogen Race Race χ2 value P valuex resistant accessions to race 5 (29.0%) was Puccinia triticina THBJy PNMQy 59.76 3.26 E-12 almost twice that found to race 1 (15.0%) P. triticina THBJy THBJz 52.10 1.31 E-10 (Table 3). In general, the level of resistance P. triticina THBJy BBBBz 30.38 4.09 E-06 exhibited in response to P. tritici-repentis P. triticina PNMQy THBJz 39.01 6.93 E-08 P. triticina PNMQy BBBBz 31.24 2.74 E-06 was not as high as that observed in re- z z sponse to powdery mildew and the rusts, P. triticina THBJ BBBB 62.32 9.4 E-13 P. graminis f. sp. tritici TTTTy TTTTz 24.99 0.0002 because only two accessions exhibited low P. graminis f. sp. tritici TTTTy TTKSz 8.82 0.066 ITs to the two races. The frequency of P. graminis f. sp. tritici TTTTy TPMKz 8.50 0.075 accessions with heterogeneous tan spot P. graminis f. sp. tritici TTTTy QCCJz 2.18 0.70 reactions was low (2.8 to 3.7%), suggest- P. graminis f. sp. tritici TTTTz TTKSz 2.46 0.65 ing a low level of heterozygosity at the P. graminis f. sp. tritici TTTTz TPMKz 7.34 0.12 resistance loci. The χ2 value obtained from P. graminis f. sp. tritici TTTTz QCCJz 2.11 0.71 z z the contingency table indicated no associa- P. graminis f. sp. tritici TTKS TPMK 18.07 0.0012 P. graminis f. sp. tritici TTKSz QCCJz 5.15 0.272 tion between the reactions elicited by race P. graminis f. sp. tritici TPMKz QCCJz 14.44 0.006 1 and race 5 of P. tritici-repentis (Table 4). Pyrenophora tritici-repentis 1 5 3.76 0.440 Marked differences were observed in re- Cochliobolus sativus 0 2 6.01 0.198 sponse to the two races of C. sativus; the Blumeria graminis UM01-05 UM01-06 8.85 0.065 frequency of resistance ranged from 0% x P value at significance level = 0.01. with race 0 to 33.6% with race 2. The y Adult plant evaluation. number of accessions exhibiting heteroge- z Seedling evaluation.

Table 3. Number and percentage of Aegilops sharonensis accessions exhibiting resistant, intermediate, susceptible, or heterogeneous reactions to seven dif- ferent fungal pathogens of wheat and corresponding values for Shannon’s diversity and equitability indicesw

x Pathogen Resistant Intermediate Susceptible Heterogeneous Total hs hs/hmax Puccinia triticina race THBJy 82 (76.6) 2 (1.9) 9 (8.4) 14 (13.1) 107 (100) 0.487 0.443 P. triticina race PNMQy 82 (77.4) 3 (2.8) 8 (7.5) 13 (12.3) 106 (100) 0.495 0.450 P. triticina race THBJz 67 (62.6) 7 (6.5) 15 (14.0) 18 (16.8) 107 (100) 0.747 0.680 P. triticina race BBBBz 64 (59.8) 2 (1.9) 17 (15.9) 24 (22.4) 107 (100) 0.674 0.613 P. graminis f. sp. tritici race TTTTy 43 (41.7) 10 (9.7) 40 (38.8) 10 (9.7) 103 (100) 0.958 0.872 P. graminis f. sp. tritici race TTTTz 14 (13.1) 5 (4.7) 75 (70.1) 13 (12.1) 107 (100) 0.658 0.599 P. graminis f. sp. tritici race TTKSz 74 (69.2) 12 (11.2) 14 (13.1) 7 (6.5) 107 (100) 0.767 0.697 P. graminis f. sp. tritici race TPMKz 35 (32.7) 20 (18.7) 45 (42.1) 7 (6.5) 107 (100) 1.043 0.949 P. graminis f. sp. tritici race QCCJz 59 (72.0) 13 (15.9) 9 (11.0) 1 (1.2) 82 (100) 0.771 0.702 P. striiformis f. sp. tritici race PST-78z 48 (44.9) 6 (5.6) 39 (36.4) 14 (13.1) 107 (100) 0.889 0.809 Blumeria graminis f. sp. tritici isol. UM05-01z 85 (79.4) 6 (5.6) 14 (13.1) 2 (1.9) 107 (100) 0.611 0.556 B. graminis f. sp. tritici isol. UM06-01z 89 (83.2) 5 (4.7) 10 (9.3) 3 (2.8) 107 (100) 0.518 0.471 Fusarium graminearum isolate KB172y 0 (0.0) 3 (2.8) 104 (97.2) 0 (0.0) 107 (100) 0.128 0.116 Pyrenophora tritici-repentis race 1z 16 (15.0) 48 (44.9) 39 (36.5) 4 (3.7) 107 (100) 1.012 0.920 P. tritici-repentis race 5z 31 (29.0) 35 (32.7) 38 (35.5) 3 (2.8) 107 (100) 1.092 0.994 Cochliobolus sativus race 0z 0 (0.0) 7 (6.5) 96 (87.9) 4 (3.7) 107 (100) 0.276 0.251 C. sativus race 2z 36 (33.6) 12 (11.2) 49 (45.8) 10 (9.3) 107 (100) 0.970 0.882 w Number given in parentheses is the percentage of that class out of the total number of accessions tested. x Shannon’s diversity index, where hs = –Σpi ln(pi) with a maximum hs = 1.099. y Adult plant evaluation. z Seedling evaluation.

946 Plant Disease / Vol. 91 No. 8 The level of diversity in A. sharonensis found in the Haifa Bay region (En HaMi- other populations from the Haifa Bay re- to the seven fungal pathogens varied con- fraz) or the northern part of the Central gion and Lebanon should be conducted to siderably; the Shannon equitability Coastal Plain (Mikhmoret and Qiryat assess the amount of diversity at the re-

(hs/hmax) values ranged from 0.116 to 0.994 Ono). No notable geographic trends were gional and population levels. (Table 3). A high level of diversity was observed for the frequency of resistance to Marked differences in diversity both found in response to P. tritici-repentis powdery mildew, spot blotch, or tan spot within and between A. sharonensis popula- races 1 (0.920) and 5 (0.994), C. sativus (Fig. 1). tions were observed in the Central and race 2 (0.882), and Puccinia graminis f. Southern Coastal Plain regions. Resistant sp. tritici races TPMK (seedling stage) DISCUSSION and susceptible accessions were observed (0.949) and TTTT (0.872 for adult). An The results of this study clearly demon- at most of the collection sites in these re- intermediate level of diversity was ob- strate that A. sharonensis is a rich and gions and for most of the diseases. More- served in response to P. striiformis f. sp. diverse source of disease resistance to over, the frequency of resistant accessions tritici (0.809), THBJ (0.680 for seedling), some of the most important pathogens of varied greatly between populations located and BBBB (0.613); P. graminis f. sp. tritici wheat. Many of the accessions exhibited a in close proximity to each other (e.g., Ash- races TTTT (0.599 for seedling), TTKS broad spectrum of resistance to the patho- dod and HaShikmim Park or Ben Zakkai (0.697), and QCCJ (0.702); and B. gens evaluated and were highly diverse in and Palmahim). A high level of interpopu- graminis f. sp. tritici isolate UM05-01 their disease reactions (Table 3). This re- lation variability in A. sharonensis also (0.556). Low levels of diversity were sult confirms previous studies document- was described by Asins and Carbonell (7) found in response to P. triticina races ing the diversity for reaction to different based on the study of three enzymatic THBJ and PNMQ (0.443 and 0.450 for fungal diseases (e.g., leaf rust, stripe rust, characters. These authors concluded that adult stage) and B. graminis f. sp. tritici and stem rust) in this species (4–6,19,58) A. sharonensis is a self-pollinated species isolate UM06-01 (0.471), due to a high and also in closely related Aegilops spp. with local adaptation over short distances. percentage of resistant accessions. A very (A. speltoides, A. longissima, A. bicornis, Diversity at the collection site level also low level of diversity was found for reac- and A. searsii) native to Israel (4,5,19). A was reported in wild barley (Hordeum tion to C. sativus race 0 (0.251) and F. high level of diversity in A. sharonensis vulgare subsp. spontaneum) at its center of graminearum (0.116) because most of the also was reported for water-soluble leaf origin (16,24). accessions exhibited a susceptible re- proteins (42), isoenzymatic characters (7), All of the Israeli accessions of A. shar- sponse. mitochondrial DNA (8), and genomic DNA onensis used in this study were derived Although the number of accessions (13,22). from a single spike. Nevertheless, we de- tested from some collection sites and re- Despite having a very restricted geo- tected heterogeneous reactions (i.e., pres- gions was low, some distinct differences graphic distribution with relatively uniform ence of resistant and susceptible plants were observed in the frequency distribu- climate and soil type, A. sharonensis pos- within the same accession) to nearly all of tion of resistant accessions within Israel sesses a high level of diversity for disease the diseases evaluated. This result suggests for some of the pathogens evaluated at the resistance that is comparable with other that the resistance loci are still heterozy- seedling stage. To leaf rust, the percentage species that have a much wider geographic gous even though this species is consid- of resistant accessions was very low in range and more widely variable environ- ered self-pollinated (26). This phenome- northern Israel. None of the accessions ments. Thus, it appears that A. sharonensis non has been reported previously in A. from the northernmost collection sites of populations are capable of maintaining sharonensis (4,5,21,37) and in other wild En HaMifraz (Haifa Bay) and Hefzi Bah sufficient genetic variability for long-term wheat (5,37,46) and barley (16) species, (Central Coastal Plain) were resistant to evolution. Geographical differences in the suggesting that it is a common feature of the two races of P. triticina (Fig. 1). In frequency of resistance were observed in wild grasses. The presence of heterozygos- contrast, the percentage of leaf rust resis- A. sharonensis despite the narrow habitat ity for restriction fragment length poly- tance for sites south of Hefzi Bah was range of the species and also the relatively morphism loci in A. sharonensis also was high, often 100% but in nearly every case small sample size from some regions. Al- reported by Dvorak et al. (13), who sug- over 40%. With stem rust, the percentage though represented with fewer accessions gested that this species may have a mixed and distribution of resistant accessions than other regions, the Haifa Bay region mating system combining self- and cross- varied according to the pathogen race. A appeared to be less diverse than the Central pollination. It should be mentioned that, high percentage of resistance to races and Southern Coastal Plain regions be- during the seed increase of accessions for TTKS and QCCJ was found at all Israeli cause no variation was observed for dis- this study, the plants were grown in close collection sites and was often 100% but ease reaction to B. graminis f. sp. tritici, P. proximity to each other within a nethouse always higher than 44%. In contrast, resis- striiformis f. sp. tritici, and P. triticina. and greenhouse. Thus, it is possible that tance to race TTTT was relatively rare; the Similar results for P. triticina were some cross-pollination might have oc- highest percentage of resistant accessions obtained by Anikster et al. (5), who sug- curred, thereby contributing to heterozy- (>50%) was found only in the northern- gested that stand density of Aegilops popu- gosity at some resistance loci. Regardless most collection site of the Central Coastal lations, rather than differences in environ- of the reason, the basis for heterozygosity Plain (Hefzi Bah) and in Lebanon. With mental parameters between regions, might in these accessions should be investigated race TPMK, a high percentage of resis- be a more critical determinant in the de- further. tance (>57%) was observed only in collec- velopment of resistance and level of diver- A. sharonensis exhibited a high percent- tions from the Central Coastal Plain sity. The fact that fewer and smaller A. age and high level (IT of 0; and 1) of resis- (Mikhmoret, Qiryat Ono, Palmahim, and sharonensis populations are present in the tance to all P. triticina races evaluated in Ben Zakkai). With stripe rust, the highest north around Haifa Bay compared with the this study (Table 3). These results are con- percentage of resistance was found at sites Central and Southern Coastal Plains (43) sistent with previous studies made at both in the Southern Coastal Plain (Nizzanim, may be a reason for the lower diversity in the seedling and adult plant stages 90%; HaShikmim Park, 60%; and Ashdod, the species. A low level of diversity also (4,5,37,46,58). The strong association 58%) and at one site in the southern half of was found for the Lebanese accessions; found for the reactions elicited by all leaf the Central Coastal Plain (Palmahim, 61%) however, no inferences can be made about rust races in pairwise comparisons sug- (Fig. 1), although some sites in these re- population diversity because details on the gests that the same gene or genes condition gions had a low frequency of resistance exact origin of these accessions are not resistance to the different races (Table 4). (i.e., Ben Zakkai, 14%, and Ziqim, 20%). known. Additional studies that include In our study, the selected races of THBJ In contrast, no resistant accessions were more accessions from En HaMifraz and and PNMQ together possess virulence for

Plant Disease / August 2007 947 13 of the 16 Lr genes included in the leaf The percentage of accessions with resis- genes for sensitivity to Ptr toxin A (race 1) rust differential set, including Lr9 (from A. tance to stem rust was lower than for leaf and Ptr toxin B (race 5). The identification umbellulata) and Lr24 (from T. ponticum) rust. Moreover, marked differences were of new races of P. tritici-repentis (31) (17). Thus, A. sharonensis accessions re- observed in the percentage of accessions highlights the need to continue research in sistant to these races are potentially valu- resistant to the different stem rust races identifying additional sources of tan spot able sources of novel Lr genes for wheat (Table 3). The lack of association between resistance for wheat, and A. sharonensis improvement. the response to P. graminis f. sp. tritici may be an important source of such resis- Leaf rust resistance in many A. shar- races in pairwise comparisons at the seed- tance. onensis accessions was effective at both ling stage (Table 4) suggests the presence As was the case for P. tritici-repentis, the seedling and adult plant stages. With of more than one stem rust resistance gene marked differences were observed in A. respect to race THBJ, the frequency of in A. sharonensis. Other investigators have sharonensis for the percentage of resistant resistance was higher at the adult plant reported resistance to stem rust in A. shar- accessions to races of C. sativus. Races 0 stage than at the seedling stage. These onensis (19) and other Aegilops spp. (A. and 2 appear to exhibit differential viru- results agree with previous reports speltoides, A. longissima, A. bicornis, and lence on wheat and barley based on pre- (6,37,58), where relatively fewer acces- A. searsii) belonging to the section Sitop- liminary studies (B. Steffenson, unpub- sions exhibited resistance to leaf rust at the sis (5,19). The presence of a variety of lished). Race 0 is avirulent on most seedling stage compared with the adult stem rust resistance genes appears to be a barleys, but is virulent on some wheats. In plant stage. Although the contingency table common feature in Aegilops spp. belong- contrast, race 2 is highly virulent on some test (Table 4) suggested that no additional ing to Sitopsis because several have been two-rowed barley lines but is mostly aviru- leaf rust resistance genes were acting at the identified in A. speltoides (e.g., Sr32 and lent on wheat. The A. sharonensis acces- adult stage, we cannot discount the possi- Sr39) and transferred into cultivated wheat sions tested in this study followed the bility of such genes acting in some A. (17,55,56). Moreover, Gerechter-Amitai same general pattern as wheat. Aldakha et sharonensis accessions because adult plant and Loegering (19) used 20 cultures of P. al. (1) studied the inheritance of spot Lr genes have been documented in the graminis f. sp. tritici and postulated 12 to blotch resistance in wheat and found that close relative A. speltoides (27). Genetic 13 different Sr genes in 44 selected acces- resistance was controlled by one or two studies on the ontogenetic expression of sions of A. sharonensis and A. longissima. genes. Given the marked differences ob- leaf rust resistance are needed to clarify Although the percentage of resistance to served in the frequency of resistance and this question. The fact that high levels of race TTTT was higher at the adult stage the ITs to the two races of C. sativus, resis- resistance to leaf rust are expressed at the than at the seedling stage, the χ2 value tance in A. sharonensis also may be con- adult stage makes A. sharonensis a possi- obtained from the contingency table indi- ferred by a few genes with major effects. ble alternative source of resistance genes cated a significant association in the reac- Although resistance to F. graminearum for wheat breeding in the northern Great tion to this race at the two growth stages has been reported in other Aegilops spp. Plains, where rust infections occur later in (Table 4). This indicates that the same (14,18), none of the accessions of A. shar- the growing season (mid-June to July). gene or genes are acting at both growth onensis screened in this study were resis- Seedling resistance also may be valuable stages. However, as discussed for leaf rust, tant to this pathogen. Only two accessions in wheat lines of the Southern Great we cannot discount the presence of adult exhibited slower and restricted disease Plains, where early infections can occur plant resistance genes acting in some A. development (intermediate reaction), but when P. triticina survives the winter. sharonensis accessions. these may not be of high value for intro- However, the use of alien genes for wheat The percentage and level of resistance to gression into cultivated wheat. In a pre- improvement is no guarantee of greater B. graminis f. sp. tritici was the highest liminary study (45), five accessions exhib- durability because the effectiveness of among all the diseases evaluated (Table 3). ited a high level of type I and type II many resistance genes derived from dip- Similar results were reported by other resistance during an initial screening test; loid wild species has been short-lived (27). investigators (21,46), albeit with a smaller however, repeat screening of progeny de- Although adult plant leaf rust resistance collection of samples. Resistant accessions rived from these plants revealed that all genes are preferred due to their greater appear to be widely distributed in Israel. individuals were susceptible. These results durability, seedling resistance genes bred Although the percentage of accessions underscore the difficulties in screening in combination with adult plant resistance resistant to the two isolates was very simi- germplasm for FHB resistance, and the can confer high levels of resistance in cul- lar, the χ2 value (0.065) from the contin- need to reevaluate accessions before reach- tivated wheat (27) that may be long lived. gency table (Table 4) suggested that resis- ing conclusive results about the presence Although only three accessions from the tance to the isolates is conferred by of resistance. Haifa Bay region were included in this different genes. This is not surprising given The highest percentage of highly resis- investigation, another study that included that the two pathogen isolates differed in tant A. sharonensis accessions (ITs of 0; 13 and 19 additional accessions from the their reaction for the resistance genes and 1) was found to the biotrophic patho- Haifa Bay (Kishon and Na’aman) and Pm3a, Pm3b, Pm3f, and Pm9 of the pow- gens of powdery mildew and the rusts. A. northern Central Coastal Plain regions dery mildew differential set. sharonensis, like other wild grasses, has (Nasholim, HaBonim, and Newe Yam), A lower frequency and level of resis- coevolved in association with the cereal respectively, was made, and only 1 acces- tance to Pyrenophora tritici-repentis was rusts and powdery mildew, being exposed sion was found to be resistant to leaf rust found in A. sharonensis, and different re- to reciprocal selection pressure (62,63). (P. Olivera and B. Steffenson, unpub- sults were obtained with the two races This long-term process occurring in the lished). This result is in agreement with evaluated (Table 3). Although no previous center of diversity (i.e., the coastal plains Anikster et al. (5) and confirms the low results have been reported regarding the of Israel) has resulted in the selection of frequency of leaf rust resistance in north- resistance of A. sharonensis to tan spot, host genotypes with different levels of ern Israeli collection sites of A. sharonen- Zhang et al. (67) found resistance (IT < 2) resistance and pathogen isolates with a sis. However, the Lebanese accessions only in A. speltoides and not in other spe- broad spectrum of virulence (54). P. tritici- exhibited a percentage of resistance that cies of the section Sitopsis, such as A. repentis also is present in the Fertile Cres- was similar to that obtained for collections longissima, A. bicornis, and A. searsii. The cent region (59) and may have co-evolved in the Central and Southern Coastal Plain differences in the ITs observed to the two with A. sharonensis in the coastal plains of regions, indicating that sources of resis- races evaluated, along with the presence of Israel, resulting in the selection of geno- tance also may be present in the northern- both chlorotic and necrotic symptoms, types with diverse resistance. Resistance to most A. sharonensis populations. suggest that A. sharonensis may carry pathotype 0 of C. sativus and F. graminea-

948 Plant Disease / Vol. 91 No. 8 rum was lacking in A. sharonensis. These sions could be selected for a gene intro- wheat. Int. J. Trop. Agric. 9:118-122. two pathogens have not been reported on gression project. Selection of accessions 11. Dill-Macky, R. 2003. Inoculation methods and evaluation of Fusarium head blight resistance wheat or on any wild grass in Israel. Thus, for a wide crossing program involving A. in wheat. Pages 184-210 in: Fusarium Head one reason for the low percentage and sharonensis also should consider specific Blight of Wheat and Barley. K. J. Leonard and level of resistance found may be due to a new and emerging disease threats to W. R. Bushnell, eds. American Phytopa- lack of co-evolution with the pathogens. It wheatlike stem rust race TTKS (48). The thological Society Press, St. Paul, MN. is interesting to note that although A. shar- frequency of resistance to this race was 12. Duvellier, E., and Dubin, H. J. 2002. Helmin- thosporium leaf blights: spot blotch and tan onensis has a similar geographic distribu- high in A. sharonensis; thus, several acces- spot. Pages 285-299 in: Bread wheat. Im- tion to A. longissima (26) and shares some sions with potentially different resistance provement and Production. B. C. Curtis, S. Ra- of the same population sites, the former alleles could be used to enhance the diver- jaram, and H. Gomez Macpherson, eds. FAO, species possesses at least some resistance sity for race TTKS resistance in wheat. Rome. to tan spot and spot blotch, whereas the In conjunction with the gene introgres- 13. Dvorak, J., Luo, M.-C., and Yang, Z.-L. 1998. Restriction fragment length polymorphism and latter species does not (57). However, re- sion effort with wheat, it also is important divergence in the genomic regions of high and sistance to both diseases was reported in A. to elucidate the genetics of resistance low recombination in self-fertilizing and cross- speltoides (57), a species that is more within the diploid species itself. Investiga- fertilizing Aegilops species. Genetics 148:423- widely distributed in the Middle East re- tions on the genetics of disease resistance 434. gion, including northern Israel. in A. sharonensis are in progress. We have 14. Fedak, G., Cao, W., Han, F., Savard, M., Gil- bert, J., and Xue, A. 2004. Germplasm en- A. sharonensis, like other wild relatives, made crosses between A. sharonensis ac- hancement for FHB resistance in spring is a potential source of novel and unique cessions resistant and susceptible to leaf through alien introgression. Pages 56-57 in: genes for disease resistance in wheat. The rust, stem rust, and powdery mildew to Proc. 2nd Int. Symp. Fusarium Head Blight. S. transfer of such genes into wheat is not determine the inheritance of resistance and M. Canty, T. Boring, K. Versdahl, J. Wardwell, routine, but is possible. Cytogenetic meth- to map the genes within this diploid spe- and R. W. Ward, eds. Orlando, Michigan State University, East Lansing. ods such as wheat-alien amphiploid pro- cies (P. Olivera and B. Steffenson, unpub- 15. Fetch, T. G., Jr., and Steffenson, B. J. 1999. duction (6) and development of wheat- lished). The information generated from Rating scale for assessing infection responses alien addition, substitution and transloca- this study will be useful in gene introgres- of barley infected with Cochliobolus sativus. tion lines may result in the successful in- sion programs and for comparative map- Plant Dis. 83:213-217. trogression of resistance genes (17,20, ping in the Triticeae. 16. Fetch, T. G., Jr., Steffenson, B. J, and Nevo, E. 25,55). Antonov and Marais (6) and 2003. Diversity and sources of multiple dis- ACKNOWLEDGMENTS ease resistance in Hordeum spontaneum. Plant Marais et al. (39) introgressed into T. aes- This research was funded in part by the Lieber- Dis. 87:1439-1448. tivum cv. Chinese Spring two genes for man-Okinow Endowment at the University of 17. Friebe, B., Jiang, J, Raupp, W. J., McIntosh, R. leaf rust and stripe rust resistance through Minnesota. We thank Y. Jin and J. Manisterski for A., and Gill, B. S. 1996. Characterization of direct hybridization and embryo rescue. their assistance in disease phenotyping; E. Millet wheat-alien translocations conferring resis- These resistance genes are fully expressed for his critical review of the manuscript; L. Lamari, tance to diseases and pests: current status. Y. Jin, and X. Chen for providing pathogen cul- Euphytica 91:59-87. in the hexaploid background and exhibited tures; and H. Bockelman and T. Payne for provid- 18. Gagkaeva, T. Y. 2003. Importance of Fusarium preferential transmission in the Chinese ing accessions of A. sharonensis. head blight in Russia and the search of new Spring background, perhaps due to the sources of genetic resistance in wheat and bar- presence of a gametocidal gene (38,39). LITERATURE CITED ley. Pages 219-222 in: National Fusarium 1. Adlakha, K. L., Wilcoxson, R. D., and Ray- Head Blight Forum Proc. U. S. Wheat Barley Gene introgression from A. sharonensis is chaudhuri, P. 1984. Resistance to leaf spot Scab Initiative. S. M. Canty, J. Lewis, and R. a long and laborious process; therefore, it caused by Bipolaris sorokiniana. Plant Dis. W. Ward, eds. would be more efficient to use an acces- 68:320-321. 19. Gerechter-Amitai, Z. K., and Loegering, W. Q. sion that carries multiple disease resistance 2. Alam, K. B., and Gustafson, J. P. 1988. Tan- 1977. 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J., accessions (591, 2172, 2173, and 1644) spp. collected in Israel. (Abstr.) Phytopathol- Browder, L. E., Hatchett, J. H., Harvey, T. L., exhibited highly resistant reactions to most ogy 82:1140. Moseman, G. J., and Waines, J. G. 1985. of the diseases evaluated in this study and 5. Anikster, Y., Manisterski, J., Long, D. L., and Evaluation of Aegilops species for resistance to would be ideal candidates for an introgres- Leonard, K. J. 2005. Resistance to leaf rust, wheat powdery mildew, wheat leaf rust, Hes- sion project with wheat. These multiple- stripe rust, and stem rust in Aegilops spp. in Is- sian fly and greenbug. Plant Dis. 69:314-316. rael. Plant Dis. 89:303-308. 22. Hegde S. G., Valkoun, J., and Waines, J. G. resistant accessions were collected from 6. Antonov, A. I., and Marais, G. F. 1996. Identi- 2000. Genetic diversity in wild wheats and three sites (Qiryat Ono, Palmahim, and fication of leaf rust resistance genes in Triti- goat grass. Theor. Appl. Genet. 101:309-316. 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